🎉 Initial commit: QQuiz - 智能刷题与题库管理平台

## 功能特性

✅ **核心功能**
- 多文件上传与智能去重（基于 content_hash）
- 异步文档解析（支持 TXT/PDF/DOCX/XLSX）
- AI 智能题目提取与评分（OpenAI/Anthropic/Qwen）
- 断点续做与进度管理
- 自动错题本收集

✅ **技术栈**
- Backend: FastAPI + SQLAlchemy 2.0 + PostgreSQL
- Frontend: React 18 + Vite + Tailwind CSS
- Deployment: Docker Compose

✅ **项目结构**
- 53 个文件
- 完整的前后端分离架构
- Docker/源码双模部署支持

🚀 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

frontend/src/utils/helpers.js

@@ -0,0 +1,117 @@
+/**
+ * Utility Helper Functions
+ */
+
+/**
+ * Format date to readable string
+ */
+export const formatDate = (dateString) => {
+  const date = new Date(dateString)
+  return new Intl.DateTimeFormat('zh-CN', {
+    year: 'numeric',
+    month: '2-digit',
+    day: '2-digit',
+    hour: '2-digit',
+    minute: '2-digit'
+  }).format(date)
+}
+
+/**
+ * Format relative time (e.g., "2 days ago")
+ */
+export const formatRelativeTime = (dateString) => {
+  const date = new Date(dateString)
+  const now = new Date()
+  const diff = now - date
+  const seconds = Math.floor(diff / 1000)
+  const minutes = Math.floor(seconds / 60)
+  const hours = Math.floor(minutes / 60)
+  const days = Math.floor(hours / 24)
+
+  if (days > 7) {
+    return formatDate(dateString)
+  } else if (days > 0) {
+    return `${days} 天前`
+  } else if (hours > 0) {
+    return `${hours} 小时前`
+  } else if (minutes > 0) {
+    return `${minutes} 分钟前`
+  } else {
+    return '刚刚'
+  }
+}
+
+/**
+ * Get exam status badge color
+ */
+export const getStatusColor = (status) => {
+  const colors = {
+    pending: 'bg-gray-100 text-gray-800',
+    processing: 'bg-blue-100 text-blue-800',
+    ready: 'bg-green-100 text-green-800',
+    failed: 'bg-red-100 text-red-800'
+  }
+  return colors[status] || 'bg-gray-100 text-gray-800'
+}
+
+/**
+ * Get exam status text
+ */
+export const getStatusText = (status) => {
+  const texts = {
+    pending: '等待中',
+    processing: '处理中',
+    ready: '就绪',
+    failed: '失败'
+  }
+  return texts[status] || status
+}
+
+/**
+ * Get question type text
+ */
+export const getQuestionTypeText = (type) => {
+  const texts = {
+    single: '单选题',
+    multiple: '多选题',
+    judge: '判断题',
+    short: '简答题'
+  }
+  return texts[type] || type
+}
+
+/**
+ * Calculate progress percentage
+ */
+export const calculateProgress = (current, total) => {
+  if (total === 0) return 0
+  return Math.round((current / total) * 100)
+}
+
+/**
+ * Validate file type
+ */
+export const isValidFileType = (filename) => {
+  const allowedExtensions = ['txt', 'pdf', 'doc', 'docx', 'xlsx', 'xls']
+  const extension = filename.split('.').pop().toLowerCase()
+  return allowedExtensions.includes(extension)
+}
+
+/**
+ * Format file size
+ */
+export const formatFileSize = (bytes) => {
+  if (bytes === 0) return '0 Bytes'
+  const k = 1024
+  const sizes = ['Bytes', 'KB', 'MB', 'GB']
+  const i = Math.floor(Math.log(bytes) / Math.log(k))
+  return Math.round(bytes / Math.pow(k, i) * 100) / 100 + ' ' + sizes[i]
+}
+
+/**
+ * Truncate text
+ */
+export const truncateText = (text, maxLength = 100) => {
+  if (text.length <= maxLength) return text
+  return text.substring(0, maxLength) + '...'
+}